diff options
| author | Bob Moore <robert.moore@intel.com> | 2008-11-12 15:15:29 +0800 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2008-12-29 22:38:36 -0500 |
| commit | fc37445733aeae4fd1a20385850620354263b1d5 (patch) | |
| tree | a989d6bf8dcc2011f25e365532c3855a48f11c62 | |
| parent | 96411a630412f057d365aa1e9de7d23c069d627a (diff) | |
| download | lwn-fc37445733aeae4fd1a20385850620354263b1d5.tar.gz lwn-fc37445733aeae4fd1a20385850620354263b1d5.zip | |
ACPICA: Add a mechanism to escape infinite AML While() loops
Add a loop counter to force exit from AML While loops if the
count becomes too large. This can occur in poorly written AML
when the hardware does not respond within a while loop and the
loop does not implement a timeout. The maximum loop count is
configurable. A new exception code is returned when a loop is
broken, AE_AML_INFINITE_LOOP. Bob Moore, Alexey Starikovskiy.
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
| -rw-r--r-- | drivers/acpi/dispatcher/dsopcode.c | 24 | ||||
| -rw-r--r-- | include/acpi/acconfig.h | 4 | ||||
| -rw-r--r-- | include/acpi/acexcep.h | 4 | ||||
| -rw-r--r-- | include/acpi/aclocal.h | 1 |
4 files changed, 29 insertions, 4 deletions
diff --git a/drivers/acpi/dispatcher/dsopcode.c b/drivers/acpi/dispatcher/dsopcode.c index 5cd406676c2c..50c892a49fa3 100644 --- a/drivers/acpi/dispatcher/dsopcode.c +++ b/drivers/acpi/dispatcher/dsopcode.c @@ -1262,13 +1262,31 @@ acpi_ds_exec_end_control_op(struct acpi_walk_state * walk_state, ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH, "[WHILE_OP] Op=%p\n", op)); - if (walk_state->control_state->common.value) { + control_state = walk_state->control_state; + if (control_state->common.value) { - /* Predicate was true, go back and evaluate it again! */ + /* Predicate was true, the body of the loop was just executed */ + /* + * This loop counter mechanism allows the interpreter to escape + * possibly infinite loops. This can occur in poorly written AML + * when the hardware does not respond within a while loop and the + * loop does not implement a timeout. + */ + control_state->control.loop_count++; + if (control_state->control.loop_count > + ACPI_MAX_LOOP_ITERATIONS) { + status = AE_AML_INFINITE_LOOP; + break; + } + + /* + * Go back and evaluate the predicate and maybe execute the loop + * another time + */ status = AE_CTRL_PENDING; walk_state->aml_last_while = - walk_state->control_state->control.aml_predicate_start; + control_state->control.aml_predicate_start; break; } diff --git a/include/acpi/acconfig.h b/include/acpi/acconfig.h index 29feee27f0ea..e50fe7157463 100644 --- a/include/acpi/acconfig.h +++ b/include/acpi/acconfig.h @@ -119,6 +119,10 @@ #define ACPI_ROOT_TABLE_SIZE_INCREMENT 4 +/* Maximum number of While() loop iterations before forced abort */ + +#define ACPI_MAX_LOOP_ITERATIONS 0xFFFF + /****************************************************************************** * * ACPI Specification constants (Do not change unless the specification changes) diff --git a/include/acpi/acexcep.h b/include/acpi/acexcep.h index 84f5cb242863..a1ae1057d2ef 100644 --- a/include/acpi/acexcep.h +++ b/include/acpi/acexcep.h @@ -153,8 +153,9 @@ #define AE_AML_CIRCULAR_REFERENCE (acpi_status) (0x001E | AE_CODE_AML) #define AE_AML_BAD_RESOURCE_LENGTH (acpi_status) (0x001F | AE_CODE_AML) #define AE_AML_ILLEGAL_ADDRESS (acpi_status) (0x0020 | AE_CODE_AML) +#define AE_AML_INFINITE_LOOP (acpi_status) (0x0021 | AE_CODE_AML) -#define AE_CODE_AML_MAX 0x0020 +#define AE_CODE_AML_MAX 0x0021 /* * Internal exceptions used for control @@ -267,6 +268,7 @@ char const *acpi_gbl_exception_names_aml[] = { "AE_AML_CIRCULAR_REFERENCE", "AE_AML_BAD_RESOURCE_LENGTH", "AE_AML_ILLEGAL_ADDRESS", + "AE_AML_INFINITE_LOOP" }; char const *acpi_gbl_exception_names_ctrl[] = { diff --git a/include/acpi/aclocal.h b/include/acpi/aclocal.h index ecab527cf78e..0323fa9aa3e6 100644 --- a/include/acpi/aclocal.h +++ b/include/acpi/aclocal.h @@ -566,6 +566,7 @@ struct acpi_control_state { union acpi_parse_object *predicate_op; u8 *aml_predicate_start; /* Start of if/while predicate */ u8 *package_end; /* End of if/while block */ + u32 loop_count; /* While() loop counter */ }; /* |